.nav>span,
.nav>a {
    color: rgb(0, 0, 0);
    z-index: 2;
    margin-left: 20px;
}

.cover {
    width: 100%;
    height: 100%;

    background-image: url(../img/cat.jpg);
    background-repeat: no-repeat;
    background-position: center center;
    background-size: cover;

    /* 为了让 .cover 和 .main 能够重叠, 给 .cover 加上个定位属性 */
    position: absolute;
    top: 0;
    left: 0;

    /* 设置了下 z 轴坐标 */
    z-index: 1;

    /* 使用 css 滤镜效果, 让背景图变的朦胧起来 */
    filter: blur(20px);
}

.login-container {
    width: 100%;
    height: calc(100% - 50px);
    display: flex;
    justify-content: center;
    align-items: center;

}

.login-dialog {
    width: 400px;
    height: 400px;
    background-color: rgba(255, 255, 255, 0.8);
    border-radius: 10px;
    border: 2px solid black;
    z-index: 2;
}

.login-dialog h3 {
    text-align: center;
    padding: 20px 0;
}

.login-dialog .row {
    width: 100%;
    height: 50px;
    display: flex;
    justify-content: center;
    align-items: center;
}


.login-dialog .row span {
    display: block;
    width: 100px;
    font-weight: 700;
}

.login-dialog #username,
.login-dialog #password {
    width: 200px;
    height: 40px;
    font-size: 20px;
    text-indent: 10px;
    border-radius: 5px;
    border: 2px solid black;
    outline: none;
}

.login-dialog .submit-row,
.login-container .registry-row {
    margin-top: 10px;
}

.login-dialog #submit {
    width: 300px;
    height: 50px;
    color: white;
    background-color: rgb(0, 128, 0);
    border: none;
    border-radius: 10px;
    font-size: 20px;
}

.login-dialog #submit:active {
    background-color: #666;
}

.login-dialog #registry {
    width: 300px;
    height: 50px;
    color: white;
    background-color: rgb(138, 235, 230);
    border: none;
    border-radius: 10px;
    font-size: 20px;
}

.login-dialog #registry:active {
    background-color: #666;
}